RE: longitude / latitude distance calculations

Karen,

What's the problem?

The code you posted is easily converted to RPG IV.  You're going to want to use 
the C runtime library to get access to the C trigonometry functions (sin, cos, 
acos, ect).  To do that, include the following h-spec: H BNDDIR('QC2LE') 
DFTACTGRP(*NO).  There's a manual that describes each function and provides a C 
prototype for it.  Translating a C prototype to RPG IV is not to tricky and 
these particular functions are quite easy.  Here's one to get you started:

C prototype
double sin(double x);

RPG IV prototype to call C function
     d sin             pr             8f   extproc('sin')
     d   radians                      8f   value


The other option, is to simply use the code in a ILE C module.  That is after 
all the beauty of ILE.  You can mix and match languages with ease.

HTH,

Charles Wilt
iSeries Systems Administrator / Developer
Mitsubishi Electric Automotive America
ph: 513-573-4343
fax: 513-398-1121
 

> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx
> [mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Karen Brasier
> Sent: Wednesday, January 12, 2005 2:23 PM
> To: 'RPG programming on the AS400 / iSeries'
> Subject: longitude / latitude distance calculations
> 
> 
> Working on a project and need to know the distance in miles 
> between two
> locations.  The information that I have in the file to use to 
> do this is the
> longitude and latitude.  I have seen the code in PC jargon, 
> but have not
> been able to find anything about how to accomplish this in RPG.    Any
> suggestions would be appreciated... I am cutting/pasting the calc to
> accomplish this below...    as I look at this, I am lost! (or 
> worse, lol)
> surely, there is an easier way, but in searching the archives, I found
> nothing on this... 
> 
> 
> 
> const pi = 3.14159265358979323846
> 
> Function distance(lat1, lon1, lat2, lon2, unit)
>   Dim theta, dist
>   theta = lon1 - lon2
>   dist = sin(deg2rad(lat1)) * sin(deg2rad(lat2)) + 
> cos(deg2rad(lat1)) *
> cos(deg2rad(lat2)) * cos(deg2rad(theta))
>   response.write "dist = " & dist & "<br>"
>   dist = acos(dist)
>   dist = rad2deg(dist)
>   response.write "dist = " & dist & "<br>"
>   distance = dist * 60 * 1.1515
>   Select Case ucase(unit)
>     Case "k"
>       distance = distance * 1.609344
>     Case "n"
>       distance = distance * 0.8684
>   End Select
> End Function 
> 
> 
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> ':::  this function get the arccos function using arctan 
> function   :::
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> Function acos(rad)
>   If abs(rad) <> 1 Then
>     acos = pi/2 - atn(rad / sqr(1 - rad * rad))
>   ElseIf rad = -1 Then
>     acos = pi
>   End If
> End function
> 
> 
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> ':::  this function converts decimal degrees to radians       
>       :::
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> Function deg2rad(deg)
>       deg2rad = cdbl(deg * pi / 180)
> End Function
> 
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> ':::  this function converts radians to decimal degrees       
>       :::
> ':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> :::::::::
> Function rad2deg(rad)
>       rad2deg = cdbl(rad * 180 / pi)
> End Function
> 
> msgbox(distance(32.9697, -96.80322, 29.46786, -98.53506, "m") & "
> miles<br>")
> msgbox(distance(32.9697, -96.80322, 29.46786, -98.53506, "k") & "
> kilometers<br>")
> msgbox(distance(32.9697, -96.80322, 29.46786, -98.53506, "n") 
> & " nautical
> miles<br>")
> 
> Karen Brasier
> I.T. Department - Software Analyst
> Standard Furniture Manufacturing Co.
> Bay Minette, Alabama 36507
> (251) 937-6741 ext 8848
> There are 10 kinds of people in the world, those that 
> understand binary and
> those that do not.
> 
> 
> 
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